Re: [ublas] ublas vector inside multi_array

From: Jesse Manning (manning.jesse_at_[hidden])
Date: 2008-02-06 16:13:07

The problem I think is that the vector class in the Ublas library does not
have an overloaded operator== function.  My guess is that operator== is not
defined in the library because its meaning could differ depending on how to
user of the library interprets equality.  You could probably write your own
operator== function so it would compile.

Simply comparing 2 ublas::vectors also fails to compile since there is no
operator== defined as shown below.

// Does not compile
namespace ublas = boost::numeric::ublas;

int main()
{
    ublas::vector<int> c(2);
    ublas::vector<int> d(2);

    for (int i=0; i < c.size(); ++i)
    {
        c(i) = i;
        d(i) = i;
    }

    if (c == d)
    {
        std::cout << "SUCCESS!!!" << std::endl;
    }

    return 0;
}

Jesse

On Feb 6, 2008 3:20 PM, Nico Galoppo <ngaloppo_at_[hidden]> wrote:

> On a related note, this fails with regular std::vector<> as well (not
> only multi_array)
>
> --nico
>
> On Feb 6, 2008 12:22 PM, Nico Galoppo <ngaloppo_at_[hidden]> wrote:
> > This test program fails to compile on my machine. Can anyone shed some
> > light on why this is happening?
> >
> > #include <boost/numeric/ublas/vector.hpp>
> > #include <boost/multi_array.hpp>
> >
> > int main()
> > {
> >   typedef boost::numeric::ublas::vector<double> T;
> >   boost::multi_array<T, 2> a,b;
> >
> >   return (a == b);
> > }
> >
> > $ g++ -I/opt/include test.cpp
> > /usr/include/c++/4.0.0/bits/stl_algobase.h: In function 'bool
> > std::equal(_InputIterator1, _InputIterator1, _InputIterator2) [with
> > _InputIterator1 =
> > boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<1ul>, const main()::T&>, _InputIterator2 =
> > boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<1ul>, const main()::T&>]':
> > /opt/include/boost/multi_array/subarray.hpp:117:   instantiated from
> > 'bool boost::detail::multi_array::const_sub_array<T, NumDims,
> > TPtr>::operator==(const boost::detail::multi_array::const_sub_array<T,
> > NumDims, OPtr>&) const [with OPtr = const main()::T*, T = main()::T,
> > long unsigned int NumDims = 1ul, TPtr = const main()::T*]'
> > /usr/include/c++/4.0.0/bits/stl_algobase.h:760:   instantiated from
> > 'bool std::equal(_InputIterator1, _InputIterator1, _InputIterator2)
> > [with _InputIterator1 =
> > boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<2ul>,
> > boost::detail::multi_array::const_sub_array<main()::T, 1ul, const
> > main()::T*> >, _InputIterator2 =
> > boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<2ul>,
> > boost::detail::multi_array::const_sub_array<main()::T, 1ul, const
> > main()::T*> >]'
> > /opt/include/boost/multi_array/multi_array_ref.hpp:273:   instantiated
> > from 'bool boost::const_multi_array_ref<T, NumDims,
> > TPtr>::operator==(const boost::const_multi_array_ref<T, NumDims,
> > OPtr>&) const [with OPtr = main()::T*, T = main()::T, long unsigned
> > int NumDims = 2ul, TPtr = main()::T*]'
> > test.cpp:9:   instantiated from here
> > /usr/include/c++/4.0.0/bits/stl_algobase.h:760: error: no match for
> > 'operator==' in
> >
> '((boost::iterator_facade<boost::detail::multi_array::array_iterator<main()::T,
> > const main()::T*, mpl_::size_t<1ul>, const main()::T&>, main()::T,
> > boost::random_access_traversal_tag, const main()::T&, ptrdiff_t>*)(&
> > __first1))->boost::iterator_facade<I, V, TC, R, D>::operator* [with
> > Derived = boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<1ul>, const main()::T&>, Value = main()::T,
> > CategoryOrTraversal = boost::random_access_traversal_tag, Reference =
> > const main()::T&, Difference = ptrdiff_t]() ==
> >
> ((boost::iterator_facade<boost::detail::multi_array::array_iterator<main()::T,
> > const main()::T*, mpl_::size_t<1ul>, const main()::T&>, main()::T,
> > boost::random_access_traversal_tag, const main()::T&, ptrdiff_t>*)(&
> > __first2))->boost::iterator_facade<I, V, TC, R, D>::operator* [with
> > Derived = boost::detail::multi_array::array_iterator<main()::T, const
> > main()::T*, mpl_::size_t<1ul>, const main()::T&>, Value = main()::T,
> > CategoryOrTraversal = boost::random_access_traversal_tag, Reference =
> > const main()::T&, Difference = ptrdiff_t]()'
> >
> >
> > --
> > Nico Galoppo :: http://www.ngaloppo.org
> >
>
>
>
> --
> Nico Galoppo :: http://www.ngaloppo.org
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